U.S. patent number 10,882,645 [Application Number 16/740,546] was granted by the patent office on 2021-01-05 for guideless resilient androgynous serial port docking mechanism.
This patent grant is currently assigned to CU Aerospace, LLC. The grantee listed for this patent is CU Aerospace, LLC. Invention is credited to David L. Carroll, Alex Ghosh, Neil Hejmanowski.
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United States Patent |
10,882,645 |
Hejmanowski , et
al. |
January 5, 2021 |
Guideless resilient androgynous serial port docking mechanism
Abstract
The Guideless Resilient Androgynous Serial Port (GRASP)
mechanism provides an androgynous mechanical and electrical
interface that can be tailored to the meet the requirements of a
given application. Each mechanism is equipped with physical
connections (spring pins) for both power and data transmission
between modules.
Inventors: |
Hejmanowski; Neil (Urbana,
IL), Ghosh; Alex (Brambleton, VA), Carroll; David L.
(Champaign, IL) |
Applicant: |
Name |
City |
State |
Country |
Type |
CU Aerospace, LLC |
Champaign |
IL |
US |
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Assignee: |
CU Aerospace, LLC (Champaign,
IL)
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Family
ID: |
71518164 |
Appl.
No.: |
16/740,546 |
Filed: |
January 13, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200223567 A1 |
Jul 16, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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62791918 |
Jan 14, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64G
1/646 (20130101); B64G 2001/1092 (20130101) |
Current International
Class: |
B64G
1/64 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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104760710 |
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Dec 2016 |
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CN |
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2013138936 |
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Sep 2013 |
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WO |
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Other References
International Search Report and Written Opinion, dated May 8, 2020,
Korean IP Office, corresponding PCT/US2020/013267. cited by
applicant.
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Primary Examiner: Davis; Richard G
Attorney, Agent or Firm: Sacharoff; Adam K. Much Shelist,
P.C.
Government Interests
GOVERNMENT CONTRACT
The invention was made woth government support with United States
Government Agency, Defense Advanced Research Projects Agency under
Contracts D16PC00182 and D17PC00307. The Government has certain
rights in the invention.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority to U.S. Provisional
Application 62/791,918 filed Jan. 14, 2019, which is hereby
incorporated herein by reference.
Claims
We claim:
1. A first guideless resilient androgynous serial port (GRASP)
mechanism for a spacecraft docking system and for use with a second
GRASP mechanism, wherein each of the first and second GRASP
mechanisms comprising: a base plate having an opening bored
through, wherein the base plate has an outward facing connection
surface configured to position against a second base plate of the
second GRASP mechanism when the first and second GRASP mechanisms
are docked together; a two-piece housing unit secured to the base
plate over the opening, the two-piece housing unit defined by a
lower housing and an upper housing, the lower housing includes a
lip surrounding the opening and a ridge extending from the lip to a
circular surface wall extending away from the base plate, and a
channel cut out is further defined along a portion of the circular
surface wall; a docking nut being positioned against the ridge and
over the opening, the docking nut having a threaded interior
surface and an exterior lower ratchet toothed section rotatably
situated within the circular surface wall of the lower housing; a
pawl mechanism being positioned in the channel cut out and biased
to engage the exterior lower ratchet toothed section to permit
rotation of the docking nut in a single direction; a docking screw
threaded into the docking nut, the docking screw having an interior
channel keyed to receive a drive shaft; a motor mechanism
configured to rotate the docking screw via the drive shaft; and
wherein the docking screw has a screw length configured to extend
through the docking nut and through the base plate when the docking
screw is in an extension position and wherein the docking nut has a
nut length configured to define a receiving space below the docking
screw when the docking screw is un-extended through the docking nut
whereby the receiving space of the docking nut is further
configured to receive a portion of a second docking screw in the
extension position when the first and second GRASP mechanisms are
docked together.
2. The GRASP mechanism of claim 1, wherein the base plate of each
of the first and second GRASP mechanisms include a plurality of
channels bored through and configured as conduits for signal ports
and signal and data pins to provide electrical and data
communications between the first and second GRASP mechanisms when
secured and connected.
3. The GRASP mechanism of claim 2, wherein the outward facing
connection surface of the base plate includes an indented surface
surrounding the opening, the indented surface being configured to
assist in the alignment when the first and second GRASP mechanisms
are secured together.
4. The GRASP mechanism of claim 3, wherein the indented surface has
a profile of a truncated cone tapered towards the opening.
5. The GRASP mechanism of claim 1, wherein the upper housing being
attached to the lower housing to secure the docking nut and pawl
mechanism in position, the upper housing includes an upper housing
opening sized over the docking nut to receive the docking
screw.
6. The GRASP mechanism of claim 3, wherein the docking screw has a
dog end configured to guide the docking screw into the opening of a
second GRASP mechanism when the first and second GRASP mechanisms
are positioned together.
7. The GRASP mechanism of claim 1 further comprising, a mounting
plate opposed to the position of the base plate and wherein a top
portion of the drive shaft is rotatably secured thereto.
8. The GRASP mechanism of claim 3, wherein the pawl mechanism in
combination with the lower ratchet toothed section of the docking
nut and the docking screw is configured to: allow one-way slip
rotation of the docking nut when the docking screw is fully
inserted through the docking nut such that a head of the docking
screw is in contact with the docking nut; and prevent the counter
rotation of the docking nut, such as when the docking screw is
inserted and rotated into the receiving space of a second GRASP
mechanism during a docking of first and second GRASP
mechanisms.
9. A first guideless resilient androgynous serial port (GRASP)
mechanism for a spacecraft docking system and for use with a second
GRASP mechanism, wherein each of the first and second GRASP
mechanisms comprising: a base plate having an opening bored
through, wherein the base plate has an outward facing connection
surface configured to position against a second base plate of the
second GRASP mechanism when the first and second GRASP mechanisms
are docked together; a two-piece housing unit secured to the base
plate over the opening, the two-piece housing unit defined by a
lower housing and an upper housing, the lower housing includes a
lip surrounding the opening and a ridge extending from the lip to a
circular surface wall extending away from the base plate; a docking
nut being positioned against the ridge and over the opening, the
docking nut having a threaded interior surface; a rotational
restriction mechanism being positioned against the docking nut
within the circular surface wall to engage the docking nut and
configured to permit rotation of the docking nut in a single
direction; a docking screw threaded into the docking nut, the
docking screw having an interior channel keyed to receive a drive
shaft; a motor mechanism configured to rotate the docking screw via
the drive shaft; and wherein the docking screw has a screw length
configured to extend through the docking nut and through the base
plate when the docking screw is in an extension position and
wherein the docking nut has a nut length configured to define a
receiving space below the docking screw when the docking screw is
un-extended through the docking nut whereby the receiving space of
the docking nut is further configured to receive a portion of a
second docking screw in the extension position when the first and
second GRASP mechanisms are docked together.
10. The GRASP mechanism of claim 9, wherein the rotational
restriction mechanism is configured to: allow one-way slip rotation
of the docking nut when the docking screw is fully inserted through
the docking nut such that a head of the docking screw is in contact
with the docking nut; and prevent the counter rotation of the
docking nut, such as when the docking screw is inserted and rotated
into the receiving space of a second GRASP mechanism during a
docking of first and second GRASP mechanisms.
11. The GRASP mechanism of claim 9, wherein the docking nut has an
exterior lower ratchet toothed section rotatably situated within
the circular surface wall of the lower housing, and wherein the
lower housing further includes a channel cut out defined along a
portion of the circular surface wall, and wherein the rotational
restriction mechanism is defined by having a pawl mechanism
positioned in the channel cut out and biased to engage the exterior
lower ratchet toothed section to permit rotation of the docking nut
in a single direction.
12. The GRASP mechanism of claim 9, wherein the rotational
restriction mechanism is defined by having a needle roller clutch
positioned in the lower housing and configured to permit rotation
of the docking nut in a single direction.
13. The GRASP mechanism of claim 9, wherein the base plate of each
of the first and second GRASP mechanisms include a plurality of
channels bored through and configured as conduits for signal ports
and signal and data pins to provide electrical and data
communications between the first and second GRASP mechanisms when
secured and connected.
14. The GRASP mechanism of claim 12, wherein the outward facing
connection surface of the base plate includes an indented surface
surrounding the opening, the indented surface being configured to
assist in the alignment when the first and second GRASP mechanisms
are secured together.
15. The GRASP mechanism of claim 9, wherein the indented surface
has a profile of a truncated cone tapered towards the opening.
16. The GRASP mechanism of claim 9, wherein the docking screw has a
dog end configured to guide the docking screw into the opening of a
second GRASP mechanism when the first and second GRASP mechanisms
are positioned together.
17. The GRASP mechanism of claim 9 further comprising, a mounting
plate opposed to the position of the base plate and wherein a top
portion of the drive shaft is rotatably secured thereto.
18. The GRASP mechanism of claim 9, wherein the base plate has an X
shape and wherein the outward facing connection surface include one
or more alignment probes and one or more alignment indented cones,
wherein when the first and second GRASP mechanisms are being docked
together, the one or more alignment probes are configured to insert
and slide within corresponding one or more of the alignment
indented cones to adjust a position of the first and second GRASP
mechanisms.
19. A docking system configured to dock two surfaces defined on
separate spacecraft, the docking system comprising at least a pair
of opposing guideless resilient androgynous serial port (GRASP)
mechanisms, wherein each of the GRASP mechanisms being positioned
on the separate spacecraft and which connect to each other to dock
the separate spacecraft together, the docking system further
comprising: a mounting platform configured on a side of separate
spacecraft, wherein the sides of the separate spacecraft being
configured for docking to each other; at least one GRASP mechanism
secured to the mounting platform of the sides of the separate
spacecraft, and wherein each of the GRASP mechanisms including: a
base plate having an opening bored through, wherein the base plate
has an outward facing connection surface configured to position
against a second base plate of the opposing GRASP mechanism when
the separate spacecraft are docked together; a docking nut being
positioned over the opening, the docking nut having a threaded
interior surface; a rotational restriction mechanism being
positioned against the docking nut to engage the docking nut and
configured to permit rotation of the docking nut in a single
direction; a docking screw threaded into the docking nut; a motor
mechanism configured to thread the docking screw through the
docking nut; and wherein the docking screw has a screw length
configured to extend through the docking nut and through the base
plate when the docking screw is in an extension position and
wherein the docking nut has a nut length configured to define a
receiving space below the docking screw when the docking screw is
un-extended through the docking nut whereby the receiving space of
the docking nut is further configured to receive a portion of a
second docking screw in the extension position when the opposing
GRASP mechanisms are docking together.
20. The docking system of claim 19, wherein the base plate of each
of the GRASP mechanisms has an X shape and wherein the outward
facing connection surface include one or more alignment probes and
one or more alignment indented cones, wherein when the first and
second GRASP mechanisms are being docked together, the one or more
alignment probes are configured to insert and slide within
corresponding one or more of the alignment indented cones to adjust
a position of the first and second GRASP mechanisms.
21. The docking system of claim 20, wherein the outward facing
connection surface, of the base plate of each of the GRASP
mechanisms, includes an indented surface surrounding the opening,
the indented surface being configured to assist in the alignment
when the separate spacecraft dock.
22. The GRASP mechanism of claim 19, wherein the docking nut has an
exterior lower ratchet toothed section rotatably situated within
the circular surface wall of the lower housing, and wherein the
lower housing further includes a channel cut out defined along a
portion of the circular surface wall, and wherein the rotational
restriction mechanism is defined by having a pawl mechanism
positioned in the channel cut out and biased to engage the exterior
lower ratchet toothed section to permit rotation of the docking nut
in a single direction.
23. The GRASP mechanism of claim 19, wherein the rotational
restriction mechanism is defined by having a needle roller clutch
positioned in the lower housing and configured to permit rotation
of the docking nut in a single direction.
Description
BACKGROUND OF THE INVENTION
Modular spacecraft concepts provide a unique challenge for docking
port design, requiring an androgynous, retractable docking port
with at least 90.degree. rotational symmetry to enable multiple
docking orientations, while supplying physical connections for both
data and power transmission. In order to enable docking in more
than two orientations, early USIP design concepts required a
combination of linear and rotary actuators which occupy a sizeable
volume and increase complexity by adding a degree of freedom to the
docking system, which will need to be restrained to secure the
dock.
The DARPA SYNERGEO Phase I effort (contract #D16PC00182) to develop
a functional docking interface design started with the existing
concepts and a literature search for past spacecraft docking port
designs. Until the turn of the century, spacecraft docking port
design was focused on human-rated technology to enable missions to
orbiting research and observation platforms such as Spacelab, MIR
and the ISS. This information provided some useful insight into the
various strategies for spacecraft approach and docking, and the
underlying technologies that enable these large, retractable and
androgynous docking solutions provided a useful starting reference
for the development of the GRASP. Shifting focus to the realm of
small satellites, there have been some interesting developments in
the last 15 years, but domestic efforts have largely eschewed
androgyny and the ability to retract in favor of emulating the
classical probe-drogue port design, which is time-tested and proven
in both space and atmosphere. Publicly available information on
recent domestic developments include the non-androgynous Mechanical
Docking System used on Orbital Express, the SPHERES androgynous but
asymmetric Universal Docking Port (UDP) demonstrated successfully
on the ISS, the Autonomous Satellite Docking System (ASDS)
developed and demonstrated by Michigan Aerospace, the AMODS
electro-magnetic docking system under development at the US Naval
Academy, and Velcro pads, which are non-androgynous and unreliable
in structural applications.
All these docking ports fail to meet SYNERGEO requirements for
symmetric androgyny. International efforts in the realm of small
satellite docking ports have yielded several concepts; two of the
relevant concepts are a semi-androgynous docking interface under
development at the University of Padova, Italy, and the port
utilized in the German iBOSS effort, which is a potential option
for the modular spacecraft concept. The port under development at
University of Padova is an innovative concept that can switch
between probe and drogue functions as needed and uses a central
spring-loaded plunger to supply the force necessary to maintain
secure docking.
SUMMARY OF THE INVENTION
The Guideless Resilient Androgynous Serial Port (GRASP) mechanism
provides an androgynous mechanical and electrical interface that
can be tailored to the meet the requirements of a given
application. Developed under the DARPA SYNERGEO program (Phase I
#D16PC00182 and Phase II #D17PC00307), assembly interfaces
comprised of a multi-GRASP array and a single mechanism have been
developed. Each mechanism is equipped with physical connections
(spring pins) for both power and data transmission between
modules.
Numerous other advantages and features of the invention will become
readily apparent from the following detailed description of the
invention and the embodiments thereof, from the claims, and from
the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee. A fuller
understanding of the foregoing may be had by reference to the
accompanying drawings, wherein:
FIG. 1 is a test apparatus equipped with four Generic Resilient
Androgynous Serial Port (GRASP) v1 prototypes (corners), this
apparatus is used to demonstrate a multi-point GRASP interface that
exhibits 90.degree. rotational symmetry normal to the contact
plane;
FIGS. 2A-2B illustrate a multi-point (2A) and single-point (2B)
GRASP interface concepts, the GRASP spring pin arrays are designed
to enable connections between identical mechanisms;
FIG. 3 illustrates the multi-point GRASP array designed for
SYNERGEO, which allows a pair of module interfaces to mate
successfully in four orientations, each established by rotating one
of the two bodies by 90.degree. about the +z axis of its interface.
In the example above, the passive body is held stationary while the
active is rotated;
FIGS. 4A-4D are illustrations of a GRASP breadboard prototype;
FIG. 5 is an exploded view of the GRASP breadboard prototype
equipped with an integrated ratchet;
FIGS. 6A-6C are illustrated views of the GRASP breadboard
prototype, shown in the `active` configuration (docking screw fully
extended); this first prototype is equipped with a ratchet to
enable androgyny, with the teeth integrated into the docking
nut.
FIG. 7 illustrates GRASP breadboard prototypes; the mechanism to
the left integrates a ratchet into the docking nut, while the
mechanism to the right uses a needle roller clutch to achieve the
desired one-way freewheel behavior.
FIG. 8 is a GRASP v1 prototype illustration;
FIGS. 9A-9C are detailed view of the GRASP v1 prototype, shown in
the `passive` configuration (docking screw fully retracted); this
prototype uses a needle roller clutch to enable androgyny.
FIGS. 10A-10D show the docking process between two GRASP
mechanisms, shown in 4 steps; the active mechanism is denoted by A,
while B is the passive mechanism.
FIG. 11 illustrate a GRASP v2 mechanism contact surface
features.
FIG. 12 illustrates a conceptual GRASP v2 drivetrain arrangement
(CONOPS sensor package not shown); and
FIGS. 13A-13D show detailed views of the GRASP v2 prototype, to be
used for the SYNERGEO single-point GRASP interface, shown in the
`active` configuration (docking screw fully extended); this
prototype uses a needle roller clutch to enable androgyny.
DESCRIPTION OF THE INVENTION
The apparatuses shown in FIGS. 1 and 2A are an equally-spaced array
of 4 GRASP v1 mechanisms 100 mounted to a structural plate 50 built
to simulate a face of a SYNERGEO spacecraft, with a single GRAPS
mechanism with a four-point connection in FIG. 2B. The array
includes power connections rated for 360 A power transmission (90 A
per mechanism) and 20 discrete pairs of low-power connections for
data transmission. The large number of low-power pins enable a
tailored approach to communications from module to module and
throughout the modular spacecraft platform based on payload
requirements for security, bandwidth, or noise. Secure mating
between modules equipped with a 4-point interface can be
accomplished using as few as two diagonally opposed mechanisms,
providing a high level of redundancy in comparison to existing
solutions.
Note that 90.degree. rotational symmetry at the interface,
illustrated in FIG. 3, is a requirement for SYNERGEO that has been
satisfied with both a multi-GRASP array and a single GRASP
mechanism. FIG. 3 shows the multi-point GRASP array designed for
SYNERGEO, which allows a pair of module interfaces to mate
successfully in four orientations, each established by rotating one
of the two bodies by 90.degree. about the +z axis of its interface.
In the example above, the passive body is held stationary while the
active is rotated. The modular and customizable features of the
GRASP mechanism 100 and interface concept provide the spacecraft
builder a variety of approaches to satisfying structural,
electrical, and morphological constraints particular to a given
application.
At a fundamental level, the GRASP mechanism 100 provides a
mechanical connection through a bolted joint. The novelty of GRASP
is the androgyny of the mechanism; a GRASP in the `passive`
configuration, FIGS. 4A-4D, has the docking screw fully retracted
and acts as the nut, while a GRASP in the `active` configuration,
FIGS. 6A-6C, has the docking screw fully extended and acts as the
bolt. This androgyny is made possible by allowing the docking nut
to rotate (freewheel) about its cylindrical axis in only one
direction.
As provided in greater detail for FIGS. 4A-6C, the GRASP mechanism
100 has a base plate 105 having an outward facing surface 107 that
would serve as the connection surface to another GRASP mechanism.
The base plate 105 also has an inward facing surface 109. The base
plate 105 has numerous channels bored through to service as
conduits 110 for the various supplies or signals, power, water,
electrical, data etc. These include various spring pins and pin
targets 116, some of which may be referred to commonly as pogo pins
used in electrical connector applications. An array 115 of these
pins would be connected on the inward facing surface 109 over the
conduits 110 and extend to the connection surface such that when
two GRAPS mechanisms were connected a full signal and supply
connection would be made (the various conduit tubing connecting to
the array is not shown). Multiple arrays may be employed as needed
or required by design.
The GRASP mechanism 100 has a housing unit 120 secured to the base
plate 105 over an opening 125 defined in the base plate 105. The
outward facing surface 107 may also include an indented surface 130
surrounding the opening 125 to assist in the alignment. The
indented surface 130 may have a cylindrical outer wall profile or
it may be tapered in a truncated cone (FIG. 9) towards the opening
125 to help guide the docking screw into the opening. The housing
unit 120 is defined by a lower housing 135 that is either secured
to the inward facing surface 109 of the base plate 105 or the lower
housing 135 may be molded with the base plate 105 as a single
unitary structure. The lower housing 135 includes a lip 140
surrounding the opening 125 with a ridge 142 extending to a
circular surface wall 144. Adjacent a portion of the circular
surface wall 144 is a channel cut out 146.
Positioned against the ridge 142 and over the opening 125 is a
docking nut 150. The docking nut 150 has a body portion 152 that
includes a threaded interior surface 154 with an exterior lower
ratchet toothed section 156. The exterior lower ratchet toothed
section 156 rotatably sits against the ridge 142 within the
circular surface wall 144. A pawl 160 and spring 162 are positioned
by a pawl pin 163 in the channel cut out 146 to engage the ratchet
toothed section allowing rotation of the docking nut 150 in only a
single direction. A docking screw 165 is threaded into the docking
nut 150.
Secured to the lower housing is an upper housing 170 used to secure
the docking nut and pawl in position. The upper housing 170
includes a bore 172 sized to receive the docking screw and the body
portion 152 of the docking nut 150.
The docking screw 165 has an interior channel 167 keyed to receive
a profiled driveshaft 180 that when inserted and rotated in either
direction will rotate the docking screw 165. The docking screw 165
may further have an extended flat top or dog end 169 used to locate
into the docking nut of the other mechanism during connection.
The driveshaft 180 is meshed to a main gear 185 further meshed to
spur gear(s) 187 and driven by a motor 190. The top 182 of the
drive shaft 180 is rotatably positioned against a bearing 184
mounted to a mounting plate 192. Posts 195 are secured between the
mounting plate 192 and the base plate 105 to secure the mounting
plate to the base plate with the motor 190 mounted between the two
plates as well.
A variety of existing technologies, (e.g. ratchet, one-way bearing,
sprag clutch), can be used in the GRASP mechanism to achieve this
one-way freewheel motion. The GRASP breadboard mechanism 100 shown
in FIGS. 4-7 implements a simple ratchet with teeth integrated into
the docking nut and a pawl mounted to the mechanism base plate.
Another iteration 200, shown on the right of FIG. 7, replaced the
ratchet teeth and pawl of the GRASP 100 mechanism with a flange,
and used a one-way bearing known (needle roller clutch) to achieve
the desired rotational limit. This approach is applied to the GRASP
v1 prototype, FIGS. 8-9C, and in the single-point GRASP interface
depicted in FIGS. 11-13.
Referring now to FIG. 9A-9C the GRASP mechanism 200 is designed
similarly to the GRASP mechanism 100, but as mentioned employs a
needle roller clutch 205 to restrict rotation of the docking nut to
a single direction.
Docking screw motion in the v1 and v2 prototypes is powered by a
COTS brushless DC micro-motor ("BLDC motor") which transmits torque
to the driveshaft via a parallel-output transmission. The motor is
sized to provide the torque required at the driveshaft to generate
the mechanical preload required by the application and maintain
sufficient margin. A variety of sensors and mechanism monitoring
strategies are used to monitor performance during actuation and
verify that joint mechanical preload requirements have been
met.
The docking process between two GRASP breadboard mechanisms,
representing one `corner` of the 4-point SYNERGEO interface, is
shown in FIGS. 10A-10D. Due to the androgynous design of the
docking mechanism, either module can be assigned the active role in
the operation. In this series of images, the active port is
designated by 100A or A, while 100B or B is the passive port.
In the first step, APPROACH, a servicing spacecraft will use its
robotic manipulators to present the incoming module for docking to
the platform in a predetermined orientation, ensuring the correct
docking ports are aligned.
In step 2, the motor of active port A will activate, advancing its
docking screw such that it threads through the ratchet nut until
the head of the docking screw contacts the ratchet nut, after which
the ratchet nut will freewheel and the docking screw with the nut
will then continue to turn clockwise. In the various embodiments of
the mechanisms discussed herein, the docking screw during its
initial rotations with rotate through a stationary docking nut.
When the docking screw is fully extending through the docking nut
and the head of the screw comes into contact with the docking nut,
continuous rotation of the docking screw causes a torque on the
docking nut such that the nut will begin to turn with the rotation
of the screw. In the embodiment of the ratchet/pawl, the teeth and
pawl are configured to prevent rotation in one direction but allow
slippage when the torque from the screw is pressed into the nut and
rotation is continued. In the embodiment of the needle roller
clutch it is the configuration of the clutch to prevent rotation in
one direction and allow rotational slippage to avoid
over-torqueing. These work perfectly in the current GRASP
mechanisms.
During the third step, ALIGN, the tip of the mechanism A docking
screw will be protruding from the side of the spacecraft, and the
screw+nut combination will continue to freely rotate clockwise as
the tip of the docking screw is brought into contact with the
mechanism B alignment cone. The tip of the screw will traverse the
mechanism B alignment cone, correcting any misalignment between the
mechanisms so docking screw A engages the threads in the mechanism
B ratchet sleeve. During cone traversal, the rotating motion of the
screw tip helps reduce contact friction at the screw/alignment cone
interface.
Once aligned, the continuously rotating docking screw+nut
combination of mechanism A will engage the threads of the mechanism
B docking nut, and the torque provided by the motor actuating
mechanism A will tighten the bolted joint and end when the target
interface preload is achieved. It is during this step that power
and data connections are made.
The transition of the spacecraft module design from a multi-point
design per spacecraft side to a single-point GRASP interface has
yielded several benefits beyond the cost savings associated with
electronics. Chief among them is a reduction in risk via
elimination of 3 mechanisms per face, along with their associated
potential failure modes. During this transition, the results of a
concurrent platform networking module the selection of Gigabit
Ethernet as the default inter/intra-modular networking solution,
which reduced the GRASP-specific conductor count for a six-port
module from >1000 to <400 (estimated; includes wires for
spring pin array, motor control and CONOPS sensor package). The
difference between the v1 prototype mechanism used for early
testing and the GRASP v2 concept is illustrated in FIG. 2.
The single-point concept meets the 90.degree. rotational symmetry
requirement and provides fine alignment during docking using a
static array of conventional probe+cone alignment features. While
the static alignment probes have the potential to shrink the
available volume for the spacecraft modules, the mass and
complexity savings of moving to a single-point interface prove an
acceptable trade.
During exploration of the single-point concept, it was determined
in an alternative embodiment to provide a GRASP mechanism with
modular spring pin arrays so that the electrical interface can be
updated as the station architecture concept evolves.
In FIGS. 11-13D, designs of a GRASP mechanism 300 are shown, with
ample space available for the spring pin array interposers. FIG. 11
depicts a contact surface of the interface with screw extended,
while FIG. 12 illustrates the drivetrain and an early mounting
bracket, designed to preserve alignment between the driveshaft and
the docking screw throughout the range of travel.
As illustrated the GRASP mechanism 300 has an X shaped base plate
305 having an outward facing surface 306 that would serve as the
connection or contact surface to another GRASP mechanism. The base
plate 305 also has an inward facing surface 309. The base plate 305
has an alignment probe 307 with corresponding alignment cones 310
that help align two GRASP mechanisms. The probes 307 when
approaching the alignment cones on a second GRASP mechanism will
ride the cones to the center aligning the two mechanisms
together.
The GRASP mechanism 300 has one way bearing mount 320 secured to
the base plate 305 over an opening 325 defined in the base plate
305. The outward facing surface 307 may also include an indented
surface 330 surrounding the opening 325 to assist in the alignment.
The indented surface 330 may have a cylindrical outer wall profile
or it may be tapered in a truncated cone 327 towards the opening
325 to help guide the docking screw into the opening. The one-way
bearing mount 320 houses the needle roller clutch 330 and the
docking nut 350. As noted above, the docking nut 350 has a body
portion that includes a threaded interior surface. A docking screw
360 is threaded into the docking nut 350.
The docking screw 360 has an interior channel 365 keyed to receive
a profiled driveshaft 380 that when inserted and rotated by an
output shaft 382 3 in either direction will rotate the docking
screw 360. The docking screw 360 may further have an extended flat
top or dog end 367 used to locate into the docking nut of the other
mechanism during connection.
The driveshaft 380 is controlled by a BLDC motor 385 with a
parallel output transmission 390 and field director 395. Posts 397
are secured between the base plate 305 and the transmission
housing. Lastly, the base plate 305 includes interface mounts 308
permitting the GRASP mechanism 300 to be secured to a surface of a
spacecraft.
As defined by the drawings herein, there is provided a first GRASP
mechanism for a spacecraft docking system and for use with a second
GRASP mechanism similarly configured. Each of the GRASP mechanisms
include:
(a) a base plate having an opening bored through, wherein the base
plate has an outward facing connection surface configured to
position against a second base plate of the second GRASP mechanism
when the first and second GRASP mechanisms are docked together;
(b) a two-piece housing unit secured to the base plate over the
opening, the two-piece housing unit defined by a lower housing and
an upper housing, the lower housing includes a lip surrounding the
opening and a ridge extending from the lip to a circular surface
wall extending away from the base plate;
(c) a docking nut being positioned against the ridge and over the
opening, the docking nut having a threaded interior surface;
(d) a rotational restriction mechanism being positioned against the
docking nut within the circular surface wall to engage the docking
nut and configured to permit rotation of the docking nut in a
single direction;
(e) a docking screw threaded into the docking nut, the docking
screw having an interior channel keyed to receive a drive shaft;
and
(f) a motor mechanism configured to rotate the docking screw via
the drive shaft.
Based on the above, the docking screw has a screw length SL
configured to extend through the docking nut and through the base
plate when the docking screw is in an extension position (FIG. 6B)
and the docking nut has a nut length NL configured to define a
receiving space 207 (FIG. 9C) below the docking screw 165 when the
docking screw is un-extended through the docking nut whereby the
receiving space 207 of the docking nut is further configured to
receive a portion of a second docking screw in the extension
position when the first and second GRASP mechanisms are docked
together (FIG. 10D).
In various embodiments, the rotational restriction mechanism is
configured to (i) allow one-way slip rotation of the docking nut
when the docking screw is fully inserted through the docking nut
such that a head of the docking screw is in contact with the
docking nut; and (ii) prevent the counter rotation of the docking
nut, such as when the docking screw is inserted and rotated into
the receiving space of a second GRASP mechanism during a docking of
first and second GRASP mechanisms.
The rotational restriction mechanisms can either be employed by a
lower ratchet toothed section on the docking nut rotatably and a
pawl mechanism positioned to engage the exterior lower ratchet
toothed section to permit rotation of the docking nut in a single
direction. Alternatively, the rotational restriction mechanism can
be defined by having a needle roller clutch positioned in the lower
housing and configured to permit rotation of the docking nut in a
single direction.
In another embodiment, the GRASP mechanism has a base plate with an
X shape and wherein the outward facing connection surface include
one or more alignment probes and one or more alignment indented
cones, wherein when the first and second GRASP mechanisms are being
docked together, the one or more alignment probes are configured to
insert and slide within corresponding one or more of the alignment
indented cones to adjust a position of the first and second GRASP
mechanisms.
As provided herein, the GRAPS mechanism are typically utilized a
part of a docking system configured to dock two surfaces defined on
separate spacecraft. The docking system includes at least a pair of
opposing guideless resilient androgynous serial port (GRASP)
mechanisms. Each of the GRASP mechanisms being positioned on the
separate spacecraft and which connect to each other to dock the
separate spacecraft together. The docking system further includes a
mounting platform configured on a side of separate spacecraft, and
wherein the sides of the separate spacecraft being configured for
docking to each other. Each surface is designed to have at least
one GRASP mechanism secured to the mounting platform. The GRASP
mechanisms are defined each to include: (i) a base plate having an
opening bored through, wherein the base plate has an outward facing
connection surface configured to position against a second base
plate of the opposing GRASP mechanism when the separate spacecraft
are docked together; (ii) a docking nut being positioned over the
opening, the docking nut having a threaded interior surface; (iii)
a rotational restriction mechanism being positioned against the
docking nut to engage the docking nut and configured to permit
rotation of the docking nut in a single direction; (iv) a docking
screw threaded into the docking nut; (v) a motor mechanism
configured to thread the docking screw through the docking nut; and
(vi) wherein the docking screw has a screw length configured to
extend through the docking nut and through the base plate when the
docking screw is in an extension position and wherein the docking
nut has a nut length configured to define a receiving space below
the docking screw when the docking screw is un-extended through the
docking nut whereby the receiving space of the docking nut is
further configured to receive a portion of a second docking screw
in the extension position when the opposing GRASP mechanisms are
docking together.
While particular elements, embodiments, and applications of the
present invention have been shown and described, it is understood
that the invention is not limited thereto because modifications may
be made by those skilled in the art, particularly in light of the
foregoing teaching. It is therefore contemplated by the appended
claims to cover such modifications and incorporate those features
which come within the spirit and scope of the invention.
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